Papers by Keyword: Concrete Technology

Abstract: Due to rapid urbanization around the world, production of cement concrete has increased several times, in turn, affect the ecosystem by the depletion of natural resources and emission of greenhouse gases. In this study, a sustainable approach has been made by partially admixing ordinary Portland cement with wollastonite micro fiber and natural fine aggregate with granite block cutting waste. The mechanical characteristics of concrete samples such as compressive strength, flexural strength, density and split tensile strength were conducted to evaluate the influence of wollastonite micro fiber and granite block cutting waste on different mixes. Different concrete mixes were casted by partially substituting ordinary portland cement with constant 10% wollastonite micro fiber and fine aggregate with granite block cutting waste at different substitution level of (0%, 10%, 20%, 30%,40% and 50%) by weight. The partial substitution of wollastonite micro fiber and granite block cutting waste enhanced the mechanical properties of cement concrete.

Abstract: Concrete is the most used man made material nowadays. The environmental impact associated with cement production is very significant due to the extent of concrete use. At the same moment cement production is associated with large energy consumption and high amount of greenhouse gas emissions. Development of concrete technology during last twenty years has lead to a significant quality shift of technical parameters and also of related environmental impacts. New types of optimized concrete mixes have significantly improved characteristics from the perspective of strength, mechanical resistance, durability and resistance to extreme loads. The use of alternative non-steel reinforcement from various types of fibres can increase reliability, durability and reduction of environmental impacts. Due to optimization of production technology, concrete is gradually becoming a building material appropriate and advantageous for sustainable construction of buildings. In this context increase of reliability and durability within whole life cycle is essential. New approaches in concrete technology like utilization of high performance and ultra high performance concretes, use of textile reinforcement, shape optimization and conceptual approach for integrated life-cycle assessment of concrete structures are presented in the paper. Some of principles are demonstrated on results of experimental research performed by author and his team at the Czech Technical University in Prague (CTU).

Abstract: The new production method for mixing and placing of high-performance concrete for thin-walled members has been transferred from laboratory to manufacturing plant and applied on real-scale elements. Planar and spatial precast elements were produced. The new technology is applicable in both building and transportation structures (panels for horizontal and vertical load-bearing structures, bridge elements, leave-in-place formwork, foundation slabs, street furniture). The material used enables significant reduction of thickness of the elements. This leads to lower weight, easier transportation and handling on the construction site, which decreases transportation and assembling costs. Further savings are possible thanks to minimized number of reinforcement bars. High durability of structures is guaranteed by the use of high-performance concrete, leading to reduced life cycle costs.

Abstract: Modern construction industry is in need of new building materials with improved operational properties. One of such materials is the sulfur-bituminous concrete – composite with matrix formed from sulfur and bitumen mix. Despite the high values of operational properties and economic efficiency of such concrete, there is the lack of necessary knowledge about technological properties of sulfur-bituminous concrete mix. The results of numerical modeling can be used to make initial decisions concerning values of control variables (relevant to mixture and technology). In the given work we present short review of the model and simulation algorithm involving particle systems as a material’s model and discuss the modeling results obtained during numerical studies of compaction process of sulfur-bitumen concrete. It is shown that for aggregates with size of one centimeter the optimal value of average thickness of the sulfur-bitumen layer is near to the one millimeter. Concrete mixes for which this condition is met can be characterized by dense structure similar to face-centered cubic.

Abstract: Concrete was used for construction in many ancient structures. Concrete technology was known by the Ancient Romans and was widely used within the Roman Empire. After the Empire passed, use of concrete became scarce until the technology was re-pioneered in the mid-18th century. The widespread use of concrete in many Roman structures has ensured that many survive to the present day. The development of reinforced concrete marked the dawn of a new age. For it was the first heterogeneous building material, using steel, cement, sand, gravel, and water. This composition possessed much better properties than each of its individual components.

Abstract: The computer simulation study of Portland cement blending confirmed the major mechanism to be size segregation in the Interfacial Transition Zones around the aggregate particles. Fine particles tend to move through the skeleton of larger particles towards the surface of the aggregate grains, improving local density. But the most interesting feature is a disproportionately larger internal bond capacity (based on van der Waals forces between nearby particles). In this contribution, we have isolated the mechanism of internal diffusion capacity of particles, on which blending efficiency relies, for a simulation study on the migration of fine sand articles into the network of coarse aggregate grains. The influences of technical parameters (including gap in size between fine sand and coarse aggregate, as well as the workability conditions) have been investigated on the migration capacity of fine sand particles. This paper will report briefly the outcomes of this computer simulation study on aggregate mix systems.